Multiple degree of freedom mobile robot loader-unloader system and method

ABSTRACT

A system for moving payloads is described. It uses one or more mobile robots. Each mobile robot comprises a payload bearing platform with a transfer mechanism with multiple degrees of freedom of movement. The system includes one or more stack exchangers having a set of alignment mechanisms, and at least one payload transfer ramp. The mobile robots pass through the stack exchanger and pick up a payload or drop off a payload.

PRIORITY

This utility application claims priority to U.S. Provisional application62/847,752, filed on May 14, 2019. The current application claimspriority as a continuation in part of U.S. application Ser. No.15/738,520 filed on Dec. 20, 2017 presently pending, which in turnclaimed priority to international PCT application PCT/US2016/039010,which in turn claimed priority to U.S. provisional application Ser. No.62/231,092, filed on Jun. 24, 2015, and U.S. provisional applicationSer. No. 62/302,070, filed on Mar. 1, 2016. The contents of eachapplication are hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The field of the invention is a system and method for optimally movingobjects on a worksite using standard mobile robots. The system allowsfor exchange of mobile robot payload while the mobile robot is inmotion, in one embodiment. In another embodiment, the robot may be inmotion or stationary but, nonetheless without the docking or alignmentprocess.

2. Background of the Invention

In various embodiments, the invention provides a system and method ofmoving inventory, empty containers, totes, orders, boxes, kits, etc.around a premises, such as warehouses and factories, without relying onfixed conveyors or other permanent infrastructure. Examples of suchavoided infrastructure include moving shelves, overhead deliverysystems, or autonomous carts moving in fixed tracks. Further, the systememploys high throughput payload exchange which does not require themobile robots to cease motion prior to receiving or depositing apayload.

In one embodiment, the invention comprises a number of mobile robotscooperating to move payloads around a known environment, such as awarehouse. Each robot includes a payload bearing platform and amechanism to release a load from the platform. The mobile robots pick upand drop off payloads at designated stack exchanger devices. The stackexchangers include means to align the mobile robots as they pass throughthe stack exchangers, automatically retrieving or depositing payloads oneach passing mobile robot. The mobile robots interact with the stackexchangers as the mobile robots remain in motion and so can pick up ordrop off payloads without stopping, in one embodiment. In anotherembodiment, mobile robots stop to wait for additional shipments. In yetanother embodiment, mobile robots stop to interact with alignmentdevices. Nonetheless, the mobile robots themselves do not have to gothrough complicated alignment procedures.

Traditionally, mobile robots interact with fixed infrastructure, such ascharging stations or conveyor belt end points following a carefulalignment process, which requires the mobile robot to move back andforth until the required alignment is achieved. This process istime-consuming and prevents the use of mobile robots for tasks thatwould require several transfers. As such, worksites are generallydesigned with large quantities of fixed conveyor belts and otherinfrastructure to move product within the worksite. This results inworksites that cannot be updated should the needs of the owner changeand are expensive to set up.

A need exists in the art for a system that allows for moving inventoryon a premises, without relying on conveyor belts and other fixedinfrastructure. Instead, the present system uses a fleet of mobilerobots. The system does not require each robot to stop all movementprior to changing the robot's payload. Further, each robot does not haveto perform highly precise alignment procedures and is instead guided bythe system elements.

SUMMARY OF INVENTION

An object of the invention is to create a system for moving payloads ona premises, such as a warehouse. An advantage of the invention is thatit allows for transport of inventory within a warehouse. An advantage ofthe invention is that it enables highly accurate inventory managementusing mobile robots.

Another object of the invention is to allow for movement of inventorywithin a warehouse without requiring significant changes to the mobilerobots, including adding many sensors. A feature of the invention isthat simple mobile robots with only minimal sensors are used. Anadvantage of the invention is that it provides new functionality for anexisting fleet of mobile robots without requiring additional sensors.

A further object of the invention is to provide a system which does notrequire new powered elements in the mobile robots. A feature of theinvention is that the mobile robots participating in the system requireonly the addition of a spring-loaded mechanism to operate with payloadexchange elements of the system. An advantage of the invention is thatmobile robots can be readily retrofitted to be included with the system.

An object of the invention is to provide a means to move inventoryaround a warehouse without requiring extensive conveyor belts and otherfixed systems. A feature of the invention is that it relies on exchangeof payloads between mobile robots at known points in the warehouse. Anadvantage of the invention is that payloads are carried large distanceswithout requiring conveyor belts.

Yet another object of the invention is to allow for efficient transfersof payloads between mobile robots. A feature of the invention is thatthe mobile robots do not have to come to a complete stop before apayload is either removed or added to the robot. A further feature isthat each mobile robot does not require precise alignment with a fixedelement prior to transferring payloads between the mobile robot and theenvironment. An advantage of the system is that mobile robots can begiven payloads or receive payloads without taking the time to stop orprecisely align with a fixed point in the infrastructure.

A further object of the invention is to provide a system which can bedeployed on demand. A feature of the invention is that the elements ofthe system, such as the mobile robots and the exchanger platforms may bedeployed on demand and are not located at fixed locations within apremises. A benefit of the system is that changes in demand for movementof goods within a premises are accommodated.

Another object of the invention is to provide a system which allows fora large number of concurrent exchanges of payloads. A feature of theinvention is that multiple exchanger platforms may be coupled to form anarray which allows for simultaneous exchange of payloads to and frommany mobile robots. A benefit of the system is that choke points withinthe premises are avoided.

An additional object of the system is to provide a fast way to movepayloads between mobile robots. A feature of the system is thatdistances between coupled exchanger platforms can be minimized as tolimit distance that payloads must travel. A benefit of the system isthat payloads are available for pickup very soon after being droppedoff.

A further object of the system is to provide a location to manipulatepayloads. A feature of the system is that in one embodiment an array ofstack exchangers includes a device to disassemble payloads as well as adevice to reassemble payloads. A benefit of the system is that it allowsfor efficient changes to payloads to be picked up or sent by each mobilerobot.

An additional object of the system is to use mechanical components inplace of active electronic ones. A feature of the invention is thatseveral elements, such as modifications to the mobile robots as well aselements in the stack exchanger are passive mechanical elements ratherthan active pneumatic or electronic ones. A benefit of the invention isthat in some embodiments, the system requires no additional electroniccomponents.

A further object of the invention is to provide a system which does notrequire special electrical connections between mobile robots and thestation where payloads are exchanged. A feature of the system is thatthe stack exchangers do not send electronic commands to the mobilerobots prior to interacting with the mobile robot payloads. A benefit ofthe system is that it does not rely on electronic signals being receivedby highly modified robots.

An additional object of the invention is to convey payloads usingadjustable stations. A feature of the system is that actuated armsdirect payloads for pick up or drop off. A benefit of the system is thatit allows for bidirectional sending or receiving of payloads on a stackexchanger.

A further object of the invention is to standardize storage within afacility. A feature of the system is that in one embodiment, it usestotes and trays to store the inventory at a facility. A benefit of thesystem is that the mobile robots interacting with the inventory can doso with precision.

An additional object of the invention is to provide a system forconveying multiple large items to a worksite on a premises. A feature ofthe system is that in one embodiment the mobile robot engages a framewhich is used to move large quantities of similar objects. A benefit ofthe system is that large quantities of bulky items may be moved to aworker at a job site with ease.

An additional object of the invention is to allow for the addition ofthe automated system to a pre-existing premises. A feature of oneembodiment of the system is that it can be implemented on any job site,including one that already has some conveyors. A benefit of the systemis that it can be deployed in both new construction as well aspre-existing warehouses.

A further object of the invention is to eliminate fixed infrastructureon the premises. A feature of the invention is that it moves inventoryand other items using mobile robots. A benefit of the invention is thatit reduces or eliminates fixed mechanisms needed to exchange payloadsand move them around the premises.

An additional object of the invention is to allow flexible exchange ofpayloads between different types of mechanisms on a premises. A featureof the invention is that mobile robots can cooperate with the stackexchangers described in this invention as well as other mechanisms, suchas applicant's RoboFrame docks, lineside delivery stations, and othertypes of inventory management systems. A benefit of the system is thatit allows for flexible handling of inventory.

A further object of the invention is to provide a system whichiteratively improves performance. A feature of the invention is thatelements of the system, such as the stack exchangers, improve with timeas the mobile robot guidance and scheduling software compensates fortime delays observed during operation of the system. A benefit of theinvention is that the mobile robots will optimize operation to travel athigher speeds and exchange payloads with less delay over time.

An additional object of the invention is to automatically verifypayloads within the system. A feature of the invention is that one ormore scales are incorporated in the stack exchangers, which confirm thatpayloads have the required weight, both at time of sending andreceiving. A benefit of the system is that it can track payloads at allstages of transmission with weight readings.

A further object of the invention is to facilitate handling of objectsor payloads that require manual review. A feature of the invention isthat by using highly flexible mobile robots, payloads or items requiringmanual review or another form of intervention (such as potentialexpiration or incorrect temperature readings), can be re-routed ondemand. A benefit of the invention is that items can be re-routed to amanual review station without a dedicated conveyor lane, as required inprior art systems.

An additional object of the invention is to provide a system whichsupport flexible payloads. In one embodiment, a large variety of stacksizes can be created (with a minimum of one container and a maximum ofsix small containers, in one embodiment). In one embodiment, up to tenempty collapsed containers may be moved using a single mobile robot. Abenefit of the system is that it can respond to changes in demand withinthe premises, as needed.

A system for moving payloads comprising: at least one mobile robot;wherein each mobile robot comprises a payload bearing platform, and apayload release latch; and at least one stack exchanger having a set ofalignment rails, a payload transfer ramp, and a latch engagement bar;wherein each said mobile robot passes through the stack exchanger andpicks up a payload or drops off a payload without fully stopping motion;wherein said stack exchanger alignment rails direct each mobile robotpayload bearing platform to reversibly engage the payload transfer rampand the stack exchanger latch engagement bar releases each mobilerobot's payload release latch during mobile robot traversal of saidstack exchanger.

BRIEF DESCRIPTION OF DRAWING

The invention together with the above and other objects and advantageswill be best understood from the following detailed description of thepreferred embodiment of the invention shown in the accompanyingdrawings, wherein:

FIG. 1 depicts an overview of the system pursuant to one embodiment ofthe invention;

FIG. 2A depicts a detailed side view of a component of the invention;

FIG. 2B depicts a schematic top view of a component of the invention;

FIGS. 2C, 2D, and 2E depict an overview of storage containers used inconjunction with the invention;

FIGS. 3A and 3B depict an overview of operation of the invention;

FIG. 4 depicts another view of an embodiment of a component of theinvention;

FIG. 5 depicts another view of an embodiment of a component of theinvention;

FIG. 6 depicts an overview of the method of use of the invention;

FIG. 7 depicts an alternative embodiment of the invention;

FIG. 8 depicts another alternative embodiment;

FIGS. 9A and 9B depict a view of further embodiments of the invention;

FIG. 10 depicts a schematic of an alternative embodiment of theinvention;

FIGS. 11A-E depict the steps of loading and unloading product from amobile robot pursuant to one embodiment of the invention;

FIG. 12 depicts an alternative embodiment of the invention;

FIG. 13 depicts an overview of an embodiment of the invention;

FIG. 14 shows a three-dimensional overview of an embodiment of theinvention;

FIGS. 15A-E depict alternative arrangements pursuant to an embodiment ofthe invention;

FIG. 16 depict details of dividers used in conjunction with oneembodiment of the invention;

FIG. 17 depicts a mobile robot overview pursuant to one embodiment;

FIG. 18 depicts the details of a mobile robot, pursuant to oneembodiment;

FIG. 19 depicts the details of another embodiment of a mobile robot; and

FIGS. 20A and B depict an overview of the action of a mobile robot armpursuant to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description ofcertain embodiments of the present invention, will be better understoodwhen read in conjunction with the appended drawings.

To the extent that the figures illustrate diagrams of the functionalblocks of various embodiments, the functional blocks are not necessarilyindicative of the division between hardware circuitry. Thus, forexample, one or more of the functional blocks (e.g. processors ormemories) may be implemented in a single piece of hardware (e.g. ageneral purpose signal processor or a block of random access memory,hard disk or the like). Similarly, the programs may be stand-aloneprograms, may be incorporated as subroutines in an operating system, maybe functions in an installed software package, and the like. It shouldbe understood that the various embodiments are not limited to thearrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralsaid elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Moreover, unlessexplicitly stated to the contrary, embodiments “comprising” or “having”an element or a plurality of elements having a particular property mayinclude additional such elements not having that property.

Overview

An overview of the system is presented in FIG. 1. As shown therein, thesystem comprises at least one mobile robot 12, the details of which willbe discussed below. While a singular mobile robot 12 is shown in FIG. 1for the sake of clarity, as implemented, the system 10 is designed tooperate a fleet of mobile robots 12. In one embodiment, the system 10operates with a minimum of one mobile robot 12 and a no theoreticalmaximum of mobile robots 12. Inasmuch as the mobile robots 12 aresemi-autonomous, and not constantly controlled by a central server, theydo not each require a wireless communication channel with a centralcontroller, and so the maximum number of robots is not set by availableradio frequency spectrum, as would be the case if the mobile robotsrequired constant direct communication. Instead, the mobile robots sharelimited communications channels, in one embodiment. In use, the quantityof mobile robots 12 used with the system 10 is optimized for the amountmovement of goods that is required by the system 10.

In one embodiment, the mobile robots 12 are substantially autonomous andselect their own routes to and from each destination within thepremises. In another embodiment, each robot's movement is subject tocentralized control.

The mobile robots 12 are designed to work with multiple stack exchangers14. FIG. 1 shows a stack exchanger 14 having two stations a and y.Multiple mobile robots 12 can interact with each station concurrently.For example, while one mobile robot 12 is dropping off a payload 20 instation a, another mobile robot 12 can be picking up a payload 20 in thesame station a.

Each station comprises one or more alignment rails 16. The alignmentrail 16 ensures that the mobile robot 12 enters the station at a correctangle. Given the shape of the robot described below, the alignment railensures that the robot will move forward through the station in theoptimum position without having to perform alignment steps, whichgenerally require the robot to slowly move back and forward. In thedepicted embodiment, the clearance between the alignment rails 16ensures that the robot can move forward through the station in only thecorrect physical configuration.

In one embodiment, not shown, each station includes additional mobilerobot 12 alignment elements, such as painted symbols on the ground. Inthis embodiment, the mobile robot 12 includes a line follower sensor,such as an infrared sensor, which will detect changes in the floorpattern. In another embodiment, the rails include hooks and otherelectromechanical elements, such as pneumatic bumpers to force themobile robot 12 into the correct configuration should it attempt toenter the station at an incorrect angle.

As the mobile robot 12 passes through the station, it does so in therobot movement direction 38. It first encounters the payload transferramp 18 which comprises two angled flanges, described below. The robotreleases the payload 20 as it passes through the station, such that bythe time it reaches the payload drop off area 26, the payload 20 istransferred from the mobile robot 12 to the drop-off area 26. Upondetecting the payload 20 in the drop off area 26, the station engages anarm or exchanger payload paddles 36 which move the payload 20 unto theshort distance payload conveyor 30.

In one embodiment, the drop off area 26 tilts to accept an incoming oroutgoing payload from a mobile robot 12.

In one embodiment, the payload conveyor 30 is a set of passive rollers,in another embodiment, the payload conveyor 30 comprises rollersrotating due to the inclusion of a motor.

The payload 20 moves on the payload conveyor 30 in the payload directionto processing 32. The payload 20 is sent to a singulator 22, which is adevice which takes the payload 20 and divides it into individualcomponents, such that the single payload can be processed as individualsubparts. In turn, these payload subparts are assembled into newpayloads by the collator 24 found in proximity to the singulator 22.

In one embodiment, the singulator 22 and collator 24 are implemented aspick-and-place devices that select components of payloads to eitherbreak up existing payloads (singulator 22) or to form new payloads(collator 24). In one embodiment, the singulator 22 and collator 24 usea common work area and a common short-term storage area such that thecomponents divided out by the singulator 22 are used by the collator 24to form new payloads 20.

One the collator 24 forms a payload 20, the payload 20 is sent in thedirection of movement from processing 34. The payload 20 is sent viaconveyor 30 to the payload pickup area 28. The payload 20 is picked upby a passing mobile robot 12.

As shown in FIG. 1, as the collator 24 can have a payload ready forpickup while the singulator 22 is working, the same robot moving througha station can drop off a payload 20 and pick up a new payload whilepassing through the station. Mobile robot 12 interactions with thepickup area 28 and the drop off area 26 occur without the robot havingto completely stop, as will be described fully below.

As shown in FIG. 1, the mobile robots 12 are designed to take the placeof fixed conveyors systems, as would be required in prior artapproaches. Each mobile robot can move a payload 20 over the samedistance as a traditional conveyor system would take. As part of thesystem 10, devices such as pick and place machines would provide theinitial payloads to the singulator 22 and collator 24 devices. After theinitial loading, the mobile robots 12 in conjunction with the stackexchanger 14 arrays can move all the inventory around the workspace.Retrieval to and from warehouse shelves is handled by another system,such as fixed arms or as described in applicant's own U.S. PatentApplication 62/302,070, incorporated herein by reference. In oneembodiment, the system includes shufflers and stackers that arrange andstack trays/totes before sending them to the stack exchanger 14. As astack is received, each is rearranged by singulator into trays/totes.The RoboFrame described in the above-listed application presents oneembodiment of a mechanism to construct and deconstruct stacks.

Mobile Robot Details

Turning to FIG. 2A, depicted therein is a side view of a mobile robot12. The mobile robot 12 comprises a robot main body 40 and a movementmechanism such as the wheels shown in FIG. 2A. The robot main body 40comprises a housing for the robot motors, encoders, sensors, and logiccontroller.

A load bearing platform 42 is supported by the robot main body 40. Inone embodiment, the platform 42 is tilt-able, in another embodiment, theplatform 42 is maintained at a constant level. The payload 20 rests onthe platform 42.

As shown in FIG. 2A, the payload 20 consists of a number of individualtotes 50 or trays (not shown) or combinations thereof as provided by thecollator depicted in FIG. 1.

The mobile robot 12 moves in the forward direction of movement 48. Thepayload 20 exerts a force against the moveable latch 44. The latch 44maintains the payload 20 on the platform 42 by preventing the payload 20from sliding off the platform 48 as the robot moves in the forwarddirection 48. The latch 44 is supported by a spring loaded mechanism 46.A downward force f on the latch 44 will move the latch 44 in thedirection of the force f, but once the force f is removed, the latchspring mechanism 46 will cause the latch to revert to an upwardposition.

As will be described in detail below, the payload 20 will slide off thebearing platform 42 if the latch 44 is disengaged. The bearing platform42 is therefore comprised of a low friction material, such as ultra-highmolecular weight plastic.

A top view of the mobile robot 12 is shown in FIG. 2B. The mobile robot12 consists of a main body curved portion 41 and main body straightportions 43 on opposing sides of the mobile robot 12. As shown in FIG.2B, the mobile robot 12 is moving in the forward direction 45.

As the mobile robot 12 encounters a station, one or more of its portions41, 43, will encounter a surface of the alignment rail 16. The mobilerobot 12 will continue to rotate while moving forward so long as therails 16 are contacting a surface other than the opposing straightportions 43. When both straight portions 43 are engaged with opposingalignment rails 16 then the robot can cease rotating.

In one embodiment, each mobile robot 12 includes a system for trackingof its present location as well as a path back to a designated temporarystorage or maintenance location. In one embodiment, this maintenancelocation is also a place to charge each mobile robot, by providingelectrical contacts embedded in a surface for corresponding electricalcontacts on the robot to recharge the robot. In an alternativeembodiment, the maintenance area includes a wireless charging substrateand each mobile robot includes a wireless charging receiver, such as aninduction receiver.

In one embodiment, as each mobile robot 12 passes through the componentsof the system, such as the exchangers 14, each mobile robot 12 ischarged as it passes over induction wireless charging elements embeddedin the stations comprising the exchangers 14.

In one embodiment, the mobile robot 12 is designed for primary movementin only one direction and its sensors and logic are optimized formovement in the one forward direction. In this way, the costs associatedwith the mobile robot 12 are minimized. Nonetheless, the mobile robot 12is capable of turning on its axis by spinning its wheels and can travelbackward, but without direct sensor input.

Container Details

FIG. 2C show details of a tote container stack which would comprise apayload 20. Each tote 50 includes a cover 54 and a tote lip 52. The totelip 52 engages a bottom surface of each tote such that a stack of thetotes comprising a payload 20 remains engaged with one another. In someembodiments, exterior side surfaces include computer-readable insignia,such as bar codes, or QR codes such that the system can track individualtotes.

In one embodiment, the tote top surface 54 is of sufficient strength tosupport two additional totes stacked on top of the top surface 54. Inthis embodiment, the totes 50 comprise a resilient plastic, capable ofcarrying heavy loads without sudden failure. In one embodiment, theplastic containers top and bottom somewhat deform and change color inthe event they are overloaded. In this way, using automated visualinspections of the totes 50, the system can determine which totes 50should be removed out of the use cycle.

FIG. 2D depicts additional product containers, using smaller trays 56instead of the totes 50 of FIG. 2C. The trays 56 include tray covers 58to lock multiple trays into one another. The trays 56 also formpayloads.

FIG. 2E depicts an additional form of product containers, open topcrates 59, having a lip in the open end wherein the flat bottom of acrate rests against the lip of the open end of a preceding crate.

In one embodiment, the payload 20 comprises a mix of trays 56 and totes50. As was discussed above, the singulator 22 and collator 24 shown inFIG. 1, are responsible for dividing out and assembling of the trays andtotes into payloads 20.

Interaction of Mobile Robot with Stack Exchanger

FIG. 3A depicts a side view of a mobile robot 12 as it passes throughthe stack exchanger 14.

The mobile robot is moving in the direction 60. At the time shown inFIG. 3A, the mobile robot 12 has passed the beginning of the payloadtransfer ramp 18, but the payload 12 remains on the mobile robot 12.Until the exchanger latch engagement bar 64 causes the mobile robotlatch 44 to be lowered, the payload 20 remains on the robot 12. Theaction of the engagement bar 64 on the latch 44 is shown in FIG. 3B,which shows a detailed view of the area designated by @ in FIG. 3A.

Once the mobile robot 12 moves through the exchanger 14, it will dropoff the load 20 and pick up the pickup payload 62 readied for the mobilerobot 12 by the collator shown in FIG. 1.

In one embodiment, the mobile robot 12 passes through the exchangerdropping off one payload 20 and picking up another payload 62 withoutstopping, and also without having to move backward and forward for themobile robot 12 to align itself. The entire process occurs within aperiod of time less than two seconds, in one embodiment. While in mostembodiments, the mobile robot 12 can exchange payloads without stopping,in other embodiments, the mobile robot 12 does stop during the payloadexchange process. In this embodiment, the stop is an opportunity toensure that the payload has been received by robot correctly, such asthrough automated visual inspection. In another embodiment, the weightof the robot and payload is measured to ensure that the expected payloadhas been provided to the mobile robot 12 and to ensure that duringloading the payload did not shift. In this embodiment, two differentscales are used on each wheel to confirm proper distribution of theweight.

In the embodiments where the mobile robot 12 comes to a stop during theloading and unloading process, the mobile robot 12 nonetheless does notrequire programming and execution of highly precise and complicateddocking maneuvers. Any stop of motion will not greatly delay the mobilerobot 12 and does not result in congestion of other robots seeking toeither load or unload payloads.

As shown in FIG. 3A, the payload transfer ramp 18 has a downwardlysloping section to help in guiding the robot payload 20 and to engagethe bottom surface of the payload 20 as it is being transferred to thepayload bearing platform 42.

The details of the interaction between the mobile robot 12 latch 44 andthe exchanger latch engagement bar 64 are shown in FIG. 3B. The mobilerobot 12, is moving in the designated direction 60 and is carrying thepayload 20. The payload 20 rests against the latch 44 payload bearingsurface 70 which holds the payload 20 in place.

As the mobile robot 12 moves in the direction 60, the latch 44 engagesthe first angled portion 72 of the latch engagement bar 64. This causesthe latch 44 to lower, in turn lowering the bearing surface 70.Eventually, the latch 44 encounters a sufficient quantity of the angledportion 72 such that it lowers the bearing surface 70 so that thepayload 20 is no longer held in place on the robot 12.

At that point, the payload 20 slides off the robot and is left on thepayload drop off area 26.

As the mobile robot 20 continues to move in the direction 60, the latch44 engages with the substantially straight portion 74 of the engagementbar 64. This straight portion 74 results in the latch 44 being loweredfully. However, once the bar 64 ends, the latch 44 returns to itsoriginal configuration due to the presence of the deformable spring 46,which will cause the payload bearing surface 70 to pop back up once theengagement bar 64 ends. In this way, as the mobile robot 12 traversesthe exchanger 14, it can drop off one load while picking up a secondload all while continuing to move forward.

Exchanger Details

Turning to FIG. 4, depicted therein is a depiction of the payloadtransfer area 90, either the pickup area 28 or the drop off area 28shown in FIG. 1. The payload transfer area 90 comprises an array of ballbearings or balls 92 which allow the payload to move in any direction.In the depicted embodiment, the ball bearings 92 are installed with adensity of 36 per square foot of the transfer area 90, in oneembodiment. However, other suitable densities are used as well.

A benefit of the system is that the same transfer area 90 can be usedfor both pickup and drop off and does not require powered components,such as motorized conveyors.

As shown in FIG. 5, the exchanger also uses a number of simple pusherarms 94. The pusher arms 94 move payload stacks from the short conveyors30, in one embodiment. The pusher arms 94 also move payloads to thetransfer area, such as the drop off area 26 shown in FIG. 5. The pusherarms 94 are simple devices which simply pop up above the surface ofeither conveyor 30 or transfer area and push the bottom of the payloadstack in the direction 96. The pusher arms 94 require only limited arange of motion and limited freedom of motion. In one embodiment, thepusher arms 94 are implemented as simple L-shaped arms where the payloadengagement portion of the L-shape can be moved up and down using a screwmechanism. In another embodiment, the payload engagement portion of thearms 94 moves up and down using a pneumatic mechanism.

Method of Use

Discussed in FIG. 6, the system comprises a method 110 of movinginventory around a warehouse or other facility without using longdistance conveyors.

The method begins with system installation tasks, which includedeploying the stack exchangers and adding the latches to a fleet ofmobile robots. In one embodiment, the number of stack exchangers at eachlocation is two, so as to allow at least one drop off and one pick uptask to occur at a time. In other embodiments, arrays of many stackexchangers are installed at multiple locations. The maximum number ofstack exchangers stations at a single location is determined by theamount of floor space available and the distances to be covered by themobile robots. Each station has an associated collator or singulator, inone embodiment. In another embodiment, a single collator and a singlesingulator are assigned to each array of stations forming stackexchangers.

The method proceeds to prime the inventory 124 of the collators. Thisallows each collator to design initial payloads for mobile robot pickup.

Once a payload is ready, a mobile robot picks up same 126. The stackexchanger collator will continue to combine available inventory foradditional payload pickups while waiting for a mobile robot to pick upthe payload.

Concurrently with the pickup, in some embodiments, and at times afterthe initial pickup, another payload is dropped off 128 at an activestack exchanger. The stack exchanger singulator breaks down the droppedoff payload to make the inventory available to the collator. Thecollator reforms a new payload 130 to be picked up by a mobile robot.The system continues to operate so long as inventory remains to bereformed into new payloads, or so long as inventory exists that requiresmovement from one location to another.

The system can enter into a power saving mode when no task is requiredof it or when no further inventory is either inbound to an exchanger orno payloads can be formed with the inventory available to the collator.

Alternative Embodiment

As shown in FIG. 7 and onwards, some inventory that requires movementaround a worksite is not suitable for movement using totes and trays.

Briefly, in prior art approaches, all the components for a particulartask are provided to a location as a single kit to be assembled. Theproblem with this approach is that it requires production of kits fromwarehouse inventory. Broken parts or missing parts in a kit will stopassembly, but may not be discovered until the assembly tasks are begun.Further, it is time-consuming to collect all the components and preparethe kits. As such, the proposed alternative embodiment allows formovement of many copies of items needed for an assembly job, withoutforming individual kits.

In place of preparing and delivering individual kits to a worker, in thesystem 150 shown in FIG. 7, a mobile robot 152, engages with a frame154. In one embodiment, the frame 154 is optimized for moving largeitems. The frame 154 includes hooks or other attachment means forholding bulky objects needed for the assembly task. The frame 154contains more than a single piece needed in the work area 162 or joblocation, where assembly project 164 is being completed.

Instead, the frame 154 containing many suitable objects 156 for the jobis brought to the work area 160. The worker may select one object 156 oras many as are needed for the task. A second mobile robot 166 is used toremove a second frame 168 from the work area 160 to a storage location.In one embodiment, a high frequency temporary storage location isdefined as separate from a long term storage or inventory storagelocation.

Each frame is made from light-weight yet durable material such asaluminum rods, PVC piping, or other rigid, yet lightweight material. Thebottom of the frame 154, 168 surface engages the top surface of thecorresponding mobile robot 152, 166.

As shown in FIG. 8, in another embodiment 180, the mobile robot 182moves a frame containing trays 184 of components. In one embodiment,each tray contains a set of components. The mobile robot 182 brings aframe 184 to a pair of alignment rails 183 where one or more trays 184is moved to the job conveyor 186. The robot may also receive one or moretrays 184 at a second sending conveyor 188. This automotive kit cantransport open pallets of goods or a bin of raw material, or evenfinished goods to another station.

As shown in FIG. 8, the transfer of the payload occurs when the mobilerobot drives in-between the shown guides. The mobile robot and itsplatform are aligned with the inbound flow rack the platform tilts sothat the mobile robot payload is deposited into the flow rack. When themobile robot is aligned with the outbound flow rack, the mobile robotplatform tilts in the opposite side to actuate the singulation device torelease the stack onto the platform.

Several exemplary combinations of a mobile robot 190 with frames 192,194, configured to convey different types of products 196, are shown inFIGS. 9A and 9B. Each is optimized to convey a specific type of bulkyproduct. As shown in FIGS. 9A and 9B, the depicted frames 192, 194 arelow-cost carts made up of a frame. Each cart is customized to carrylarge items without damage and present them to the operator in anergonomic way. In one embodiment, the frames 192, 194 include RFIDidentifiers and the system uses the RFID identifiers to identify thecart, the cart type, content, and location.

Alternative Embodiment

In an alternative embodiment 200, shown in FIG. 10, a mobile robotcomprises a top platform which includes a right angle transfer mechanism214. In one version, the transfer mechanism 214 is added on top of anexisting mobile robot, such as robot 12 shown in FIG. 1. In analternative embodiment, the mechanism 214 is integrally molded with therobot.

The mechanism 214 is attached to the top of the robot. The right angletransfer mechanism 214 allows for transfer of a payload carried by themobile robot from the mobile robot to a fixed platform, in someembodiments. The payload is transferred to stack handlers, as describedthe above embodiments. In some instances, payloads can only be handledin a particular manner, such as being transferred only from the front ofa mobile robot, for example when the mobile robot is interacting withvarious articulated robotic arms.

The end results of this embodiment 200 is that a mobile robot cantransfer its payload to a variety of receiving stations, with at leasttwo degrees of freedom without using a loading or unloading arm. Insteadthe surface transfer mechanism 214 on each robot rolls the payload offthe mechanism 214 by using alternative sets of rollers. Some rollers 215cause the payload to move in a first direction a whereas other rollers217 cause the payload to move in a second, different direction p. Eachdirection is depicted as an arrow accompanying the drawing.

In one embodiment, the mobile robot can selectively engage varyingnumbers of the rollers 215, 217 creating a variety of motion ofpayloads.

Turning to FIGS. 11A-E, a process of loading and unloading of mobilerobots is depicted therein. As shown in FIG. 11A, a mobile robot 210engages with a guide rail 222 on its way to interact with a stackexchanger 220.

The mobile robot 210 is carrying a payload 216 in the direction of thestack exchanger 220, making progress to its destination when comparingFIG. 11A to FIG. 11B. As shown in FIG. 11C, the mobile robot 210 doesnot need to rotate around the guide rail 222 as it nears the stackexchanger 220 as the transfer mechanism shown in FIG. 10 allows eachmobile robot to approach the exchanger 220 from any direction.

FIG. 11D depicts the mobile robot 216 when it has reached the drop offposition at the stack exchanger 220. The mobile robot 210 does not leavethe rail 222 during this process. As shown in FIG. 11E, the mobile robot210 transfers the payload 216 to the stack exchanger by passing thepayload 216 from the side of the mobile robot 210.

As shown in FIGS. 11A-E, the guide rail 222 is shown as allowing therobots to enter from one direction but exit in either direction. Whilein one embodiment the guide rail 222 comprises a physical feature in thefloor of the facility that protrudes from the floor, in otherembodiments the guide rail is a high contrast line that is observed bythe mobile robots 210. In another embodiment, the guide rail 222 is avirtual feature that exists only in the internal maps of the facilityused by the mobile robots 210. Further, while in FIGS. 11A-E the rail222 is shown as a single line, as used in some embodiments the rail 222comprises a set of matching rails that engage the mobile robot 210.

Additional Embodiments

Additional embodiments are shown beginning with FIG. 12.

These additional embodiments improve the production throughputcapabilities of the system. For example, in one embodiment, the systemis able to receive 16 trays of product per minute and pack up to 43trays and totes per minute.

As shown in FIG. 12, the embodiment 250 comprises a mobile robot 252where trays or totes (not shown) are unloaded 254 or loaded 256 using areceiving area 260 of a stack exchanger 258. A benefit of the embodiment250, as depicted in FIG. 13, is that multiple receiving areas 260, 262,264, can be added to a single stack exchanger 258. In the embodiment ofFIG. 13, two mobile robots 252, 266, can interact with the stackexchanger 258 at the same time. This way, the throughput of the systemis increased significantly, without having to increase the number ofstack exchangers in a facility. As described herein, the stackexchangers include the most expensive components, such as roboticpicking arms, cameras, sensors, and other expensive equipment. A threedimensional view of the embodiment 250 from FIG. 12 is shown in FIG. 14.The path taken by the trays or totes 270 is shown in FIG. 14.

FIGS. 15A-E depict different arrangements of stack exchangers. Thearrangements of stack exchangers result in varying performancecharacteristics for the system. The details are summarized in thefollowing table:

Containers/minute/stacker set (point of entry) Configuration FIG. 15A15B 15C 15D 15E Not Shown Configuration One Parallel, Two Parallel, OneParallel, Two Parallel Two Parallel Three Parallel Description Two inSeries One in Series Three in Series (One + Two in Series) Two in SeriesOne in Series # stacker/ 2 2 3 3 4 3 destacker pairs # points of entry 12 1 2 2 3 Receiving 16  8.0 N/A N/A N/A N/A Pack N/A N/A 43   28.6  21.5 14.3

As can be appreciated from FIGS. 15A-E and the above table, theconfiguration of the stacker/destacker elements is important indetermining the throughputs of a module. As shown in the figures, thestacker/destackers can be connected in series wherein they are daisychained such that there is one point of stack entry and transfer intothe module. Alternatively, they can also operate in parallel effectivelyconnecting into the module at different locations to provide more pointsof stack entry. Application for this is limited by the need to keep themobile robot traffic for the parallel stacker separated. In someembodiments, no account is made for parallel stacker sets that causesmobile robot flows to impact each other. In one embodiment, one way toincrease parallel stacker transfer is to use two lower though putmodules instead of one high throughput module.

In implementing the payload exchange systems, in some embodiments, asingle side transfer has the same or better throughput than two endtransfer cells, but this approach is difficult to scale with multipleserial stack handlers. The average number of containers/stack has a bigimpact on the applicability of the different concepts and/or options forstacker configuration which in turn has an impact on the module design.

FIG. 16 depicts some approaches to help direct the mobile robots to thecorrect receiving area. In FIG. 16 dividers 272, 274 direct the mobilerobots 252, 266. The mobile robots 252, 256 remain in a mobile robottraffic space 276 with a two-lane entrance and exit area 278.

The arrangements of the stack exchangers and mobile robots have severalbenefits.

Some conveyors are rated to 100 KG stacks whereas other conveyors suchas ones which handle only loading and unloading are rated at 50 KG. Insome embodiments, depending of stack size limits any stack, eachconveyor may be limited to approx. 60 KG

The stack exchanger conveyor uses higher quality parts and is thereforemore reliable than the loading and unloading conveyor. In someembodiments, a conveyor will have lower power consumption due to lessaxis to lock and opportunity to add roller brake. Front load conveyorwill allow more space to incorporate active stack barriers than a sideload design as the loads are generally rectangular and so the front loadconveyor is smaller.

Another benefit of a front load only design is that the mobile robot canhave fixed side stack barriers. Some of the embodiments shown in thefigures use conveyor design which provides more opportunity to usepermanent cart design. which would increase mobile robot capacity andaverage containers/stack. A high capacity mobile robot 280 is shown inFIG. 17. The details of the high capacity mobile robot barriers aredescribed in the following figures.

Mobile Robot Barriers

Turning to FIG. 18, depicted therein is a high capacity mobile robot 282with at least one fixed side barrier 284 and a moveable front barrier286.

The side barrier 284 is not moveable in the embodiment 282 shown in FIG.18. The side barrier 284 comprises two bars 285, 288 extending upwardlyinto a v-shape. One end of the bars is fixed to the base 292 of themobile robot while the opposing end of the bars are joined together.

The front barrier 286 uses a single vertical member 288 and a moveablearm 290. The arm pivots to a configuration up away from the base 292 ofthe mobile robot or towards the vertical member 288. The open and closedconfigurations are shown in subsequent figures.

As shown in FIG. 18, with the side and front barriers, the mobile robotcan be loaded with a variety of containers 294.

In one embodiment, the front opening barrier comprises a single axis armand whose length covers all tray and tote combinations. A benefit ofthis embodiment is that minimal space requirement when docked. The armis counterbalanced with a spring to ensure failsafe operation. In oneembodiment, a small motor gearbox retract the arm. In one embodiment asafety switch provides input to the controller or the status of the armis in series with mobile robot drive power, to ensure that the mobilerobot does not move while the arm is retracted.

In the depicted embodiment, the fixed side barrier is shown as a vshape. In other embodiments, multiple design options can be used. Asshown, the barrier is lightweight minimal support. It allows easier fastsafe loading from stack handler where the side transfers occur from theopposite side which remains open.

The embodiment shown in FIG. 19 includes only one fixed rear barrier296. While again in the embodiment 294 of FIG. 19 a v shape is used forthe barrier, multiple design options are possible. As shown, the barrierprovides lightweight minimal support and stops stack tipping whenaccelerating and while the mobile robot is traveling on a gradient. Thebarrier allows easier fast safe loading from stack exchanger orroboframe. In the embodiment 294 of FIG. 19, the sides remain open withno barriers. This design assumes main front to back rollers are engagedand held. In this embodiment, friction prevents sliding of the stackduring turning of the mobile robot.

FIG. 20A shows an overview of the mobile robot with the front arm closedwhich allows for safe movement of the mobile robot. FIG. 20B shows thefront arm opened, which is necessary during transfer of the contents ofthe mobile robot, in one embodiment.

Although exemplary implementations of the invention have been depictedand described in detail herein, it will be apparent to those skilled inthe relevant art that various modifications, additions, substitutions,and the like can be made without departing from the spirit of theinvention and these are therefore considered to be within the scope ofthe invention as defined in the following claims.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. While the dimensions and types ofmaterials described herein are intended to define the parameters of theinvention, they are by no means limiting, but are instead exemplaryembodiments. Many other embodiments will be apparent to those of skillin the art upon reviewing the above description. The scope of theinvention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the terms“comprising” and “wherein.” Moreover, in the following claims, the terms“first,” “second,” and “third,” are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. § 112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

The embodiment of the invention in which an exclusive property orprivilege is claimed is defined as follows:
 1. A system for movingpayloads comprising: at least one mobile robot; wherein each mobilerobot comprises a payload bearing platform, main body straight portionsadapted to be engaged with alignment rails; and at least one stackexchanger having at least one payload transfer ramp and alignment rails;wherein each said mobile robot passes through the stack exchanger andpicks up a payload or drops off a payload; wherein each stack exchangercomprises multiple payload transfer ramps wherein each transfer ramp iscapable of loading and unloading a mobile robot; wherein each mobilerobot payload bearing platform comprises alternative sets of rollers,each set of rollers moving a payload in a different direction.
 2. Thesystem of claim 1 wherein said mobile robot alternative sets of rollersmove a payload off the mobile robot payload bearing platform.
 3. Thesystem of claim 1 further comprising an array of stack exchangersarranged in close proximity wherein each stack exchanger is designatedeither to pick-up or drop-off of payloads.
 4. The system of claim 3wherein each array of stack exchangers further includes a collator tocombine dropped off payloads for pickup by a mobile robot.
 5. The systemof claim 3 wherein each array of stack exchangers further includes asingulator to split up dropped off payloads for pickup by a mobilerobot.
 6. The system of claim 1 wherein the mobile robot can selectivelyengage varying numbers of the rollers comprising the alternative sets ofrollers.
 7. The system of claim 1 wherein each stack exchanger furthercomprises a payload conveyer and adjustable arms wherein said stackexchanger adjustable arms move payloads between the stack exchanger'sdrop off area and the payload conveyer.
 8. The system of claim 1 furthercomprising dividers which direct multiple mobile robots to a specificpayload transfer ramp.
 9. The system of claim 8 wherein at least onepayload conveyer connects different stack exchangers comprising an arrayof stack exchangers.
 10. The system of claim 1 wherein each stackexchanger further comprises payload conveyer payload paddles whereinsaid stack exchanger payload paddles move payloads between the stackexchanger's drop off area and the payload conveyer.
 11. The system ofclaim 1 wherein each said mobile robot passes through the stackexchanger and picks up the payload or drops off the payload withoutfully stopping motion.
 12. The system of claim 1 wherein each saidmobile robot makes at least one stop as it passes through the stackexchanger and picks up the payload or drops off the payload.
 13. Thesystem of claim 1 wherein each said mobile robot passes through thestack exchanger and picks up the payload or drops off the payloadwithout moving backward to perform alignment procedures.
 14. The systemof claim 1 wherein each mobile robot comprises a moveable barrier. 15.The system of claim 1 wherein each mobile robot comprises at least onefixed barrier.